Ignition timing signal generator

ABSTRACT

An ignition timing signal generator for use in a contactless ignition system for internal combustion engines is provided with a first and a second timing core disposed in the rotor of a magneto generator in the system and a magnetically shielded timing signal pickup means mounted on the stator of the magneto generator for generating an ignition timing signal when the pickup means is magnetically coupled to the timing cores.

U d States Patent 1191 Fujii 310/70 Nagasawa Nov. 27-, 1973 [54] IGNITION TIMING SIGNAL GENERATOR 3,398,353 8/1968 Noddin 322/91 I 1 3,405,347 10/1968 Swift 322/91 [75] Invent Nagasawa, Japan 3,258,550 6/1966 Guetersloh 310/70 73 Assigneez Nippondenso Co. Ltd. Aichhken 3,198,974 8/1965 Dusenberry 3l0/70 Japan Prima Examiner-R. Skud 22 F] 197 y Apr 28 2 Attorney-John W. Malley et al. [2]] Appl. No.: 248,489 7 v 57 ABSTRACT [30] Foreign Application Priority Data J Apr. 28 1971 Japan 46/34050 ignition timing signal generator use in a tactless ignition system for internal combustion en- 521 US. Cl. 310/70 322/91 is Pmvided with a first and a Sewn! timing we 51 Int. Cl. mizk 9/00 dislmsed a magnem the 5s F1610 of Search.....- 310/70 67 153' system and a magnetically Shielded timing Signal 0/156. 3' pickup means mounted on the stator of the magneto I generator for generating an ignition timing signal ['56] References Cited when the pickup means is magnetically coupled to the UNITED STATES PATENTS 3,641,377 2/ 1972 6 Claims, 11 Drawing Figures PAIENlEum lvzmn I r 3,775,627

sum 10m FIG. 20 FIG. 2b

PATENTEDuuvzmn 75 SHEET- 0F 4 FIG. 3

FIG. 5'

IGNITION TIMINGSIGNALGENERATOR FIELD OF TI-IEI'INVENTION This invention relates to a magneto generator type contactless ignition system for internal combustion engines mounted on automotive vehiclesand the-like, and

more'particularly to an ignition timing signal generator for usein a capacitor charge-discharge type ignition system. i I v I SUMMARYOF THE INVENTION It is-a primary object of the present invention to provider-in a contactless ignition-system for internal combustion engines, a novel anduseful ignition timing signal generator whose rotor is common to .the rotor'of-a magneto generator servingasv acapacitor charging orlamp energizing power supply.

In accordance with the present invention, there is provided, in a contactless ignition system for an internalcombustion engine including aumagneto generator havinga rotor and a statorforsupplyingelectricpower for ignition, an ignition timing signalv generatorcomprising a first timing core coupled toone of the 'magnetic poles in the rotor of said -magneto-generator, a second timing core disposed adjacenttosaid first .tim-

ing core and coupled .toa .generallyxcup-shapedbody forming the outer-casing of said rotor,: and amagneti- ;cally shielded timing signal pickup "means disposed in the stator of said magneto generator so that said first andsecond timing cores canxbe cyclically brought opposite to said'pickup means duringrotation of said ro- BRIEF DESCRIPTION OFT-HE DRAWINGS FIG. 1 is an electrical circuit diagram of a capacitor charge-discharge type ignition systememploying'a timing signal generator according to the present invention.

FIGS. .2a and 2bsh ow the mannerof mounting a'first anda second timing core of the timing signal generator of 'the present invention in the rotor of 'a'magneto gner- DESCRIPTION OF THE PREFERRED EMBODIMENT )FIG. 1 shows the structure of a capacitor chargedischarge type ignitionsystem including therein an ignition timing signal-generatorof' the present inventionfor determining the ignition 'timingof a single cylinder engine. Referring to FIG. 1 voltage generated across an armature l of a magneto generator, which serves as an ignition power supply, is rectified by a rectifier '2'to charge a capacitor 3 through a circuit including'a diode 6. A controlled rectifier or'thyristor conducts in response to the application of a'signal appearing across a coil 4' of the timing signal generator and the charge stored in the capacitor 3 is discharged through a circuit including a primary winding 7a of an ignition coil 7 and the thyristor 5. A high voltage is induced in a secondary winding 7b of the ignition coil 7 and an'ignition spark jumps across the spark gap'of an ignition plug P. A diode 8 is provided for protecting the against damage.

The structure of the timing signal generator embodying-the present invention will now be described with reference to FIGS. 2a, 2 b, 3 and 4. The magneto gener ator includes a stator and a rotor which are arranged as shown in FIGS. 3 and 4, and the rotor of the magneto generator'is common to the rotor of the timing signal generator according to the present invention. More precisely, the rotor comprises a generallycup-shaped bodyfll 0 of iron and a plurality of pairs of pole cores 1 1 andmagnets 12, each polecore 11 being in the form of a plate of magnetic material such as iron..These pole cores 11 and magnets 12 are disposed on the-inner-peripheral surface of the cup-shaped body 10 in an equally circumferentially spaced relationship and are secured to such surface of the cup-shaped body 10 by a casting 15 of light alloy. In:accordance with the present invention, a member 13 of' magneticmaterial such as .ironhaving a shape as shown in F IGS.'2a and 2b is contacted on or welded, riveted or otherwise fixed to one end of the pole cores 11 and the inner surface of the cup-shaped body respectively and'is partly embedded in the casting 15 of light alloy. Then, a U-shaped portionl3' of the member 13 is cut off (e.g., along the dashed arc line shown in FIG. 2a) by a cutting tool to divide the member 13 into a first timing core 13a and a separate second timing core 13b so'that the inner end portions of these timing cores 13a and 13b serve as timing poles such as best shown in FIG. 20. It will be seen thata predetermined distance can be maintained between these timing poles due to the fact that the portions 13a and 13b have been an integral part of the member 13 before the cutting operation to remove "the U-shaped'portion 13'. Further, the sectional area of the timing cores 13a and 13b is relatively small to such an extent the they are easily magnetically saturated. Thus these timing cores 13a and 13b would not hardly adversely affect the magnetic flux emanating from the pole core 11 and the reduction in the magneticfluxdue to the timing cores 13a and 13b is almost negligible.

The stator comprises a lamp energizing and battery charging armature l and anignition power supply armature 17 which are disposed opposite to each other on a stationary base plate 16 as seen in F IG.4. A timing signal pickup means 4 is disposed on the stationary base plate 16 between these armatures l and 17 at a position corresponding to the timing cores 13a and 13b. As seen in FIGS. 3 and 5b, the timing signal pickup means 4 comprises a magnetic shielding casing 14a of magnetic material such as iron and a pickup coil 4' wound around aniron core 14b disposed within the casing 14a. The rotor and the stator are assembledin such a state that the outer end faces of themagnetic shielding casing 14a and iron core 14b in the stator are opposite to the pole face portions of the timing cores 13a and 13b in the rotor in the relative positions'shown in FIGS. 3 and 4.

In the aforementioned embodiment, the timing cores 13a and 13b are described as being made from an integrally formed member 13 embedded in thecasting 15 of light alloy together'with the pole core 11 bycutti'ng thyristor 5 first timing core 13a integrally with the pole core 11 from a sheet of magnetic material, forming the second timing core'l3b with an integral elongated portion 1311 at one end thereof and with a notch l 3b 'bycutting off a portion thereof, fitting the integral member of the .timing core'l3a and the pole core 11 on a-predetermined position of the cup-shaped body 10, fitting the second timingcore 13b having the elongated portion 13b in a predetermined spacialrelation with the. integral member by welding or by holding the elongated portion 1312 with a jig or the like while locating the other end of the timing core 13b in contactwith the inner surface of the cup-shaped body 10, embedding the integral member of the timing core 13a and the pole core 11 together with the second timing core 13b in a casting of light metal, and cutting off the elongated portion 13b. In this embodiment, the timing core 13b is protected from flying off by a centrifugal force during rotation thereof by virtue of theengagement between the notch and the casting .15, whereby the axial length of; the cup-shaped body may beshortened compared with that in the first-mentioned embodiment in which the timing core 13 is necessary to be completely buried inthe casting l5.

The operating principle of the timing signal generator according to the present invention will be described with reference to FIGS. 50 to d. In FIG. 5a, one of the magnetic poles ofthe rotor having the timing cores 13a and the cap-shaped body 10, and H is the magnetic potential difference between the pole portions 13a and 13b of thev respective timing cores 13a and 13b. Then, the magnetic potential varies along the curve a in the case of the former, while the magnetic potential varies alongthe curve b in the case of the latter as shown in FIG. 5b. When now the pole portions 13a and 13b of the timing cores 13a and 13b in the rotor are brought opposite to the outer end faces of the magnetic shielding casing 14a and iron core 14b of the timing signal pickup means 4 respectively during rotation of the rotor, a magnetic flux corresponding to the magnetic potential difference H, above described passes through the iron core 14b. In this case, a magnetic potential difference H, is applied to the timing signal pickup means 4 by the power generating pole. However, since the ratio of H; to H is sufficiently large, the operation of the timing signal pickup means 4 is not substantially affected by the power generating pole. The provision of the magnetic shielding casing 14a is effective in cancelling the magnetic potential difference I-Ig applied thereto by the power generating pole so that the iron core 14b, hence the coil 4' wound around the iron core 14b within the magnetic shielding casing 14a is not in any way adversely affected by the magnetic flux ema nating from the power generating pole. Further, the

magnetic flux passing through the iron core 14b is not reducedin any way by the magnetic'shielding casing 14a due to the fact that the pole portions 13a and-13b of the timing cores 13a and 13b are entirelyincluded within the area covered by the magnetic shielding casing 14a in the position shown in FIGS. 5a and 5b. It will be seen therefore that the provisionof the magnetic shielding casing 14a is effective in that the magnetic flux emanating from the timing cores 13a and 13b is solely applied to the iron core 14b.

Suppose, for convenience of explanation, that-the rotor is fixed'and the timing signal pickup means 4 is -moved from right to left relative to the rotor as shown by the arrow in FIG. 5b, the engine rotating in the'normal direction in such a relationship between the rotor and the pickup means 4. In this case, the magnetic flux passing through the iron core 14b varies locally in substantially sinusoidal fashion as shown in FIG. 5c, and a voltage of pulse waveform having a large amplitude in one polarity as seen in FIG. 5d appears across the pickup coil 4. Suppose, for example, that the pole portions 13a and 13b of the timing cores 13a and 13b are spaced apart by a distance of l mm from each other, and the circle drawn by these timing cores 13a and 13b has a diameter of mm, then the pole portions 13a and 13b of the timing cores 13a and 13b pass over the iron core 14b over an angle 0 which is given by 0 l/80 1r 360= 1.43 Thus, the timing signal generator can generate a sufficiently large output even when the engine is rotating at a low speed. Variations in the ignition timing can be selected to lie within 6 in FIG. 5d. In other words, the variations in the ignition timing lie within a very narrow range of 0/4 0.36", so that the ignition timing can be.satisfactorily stabilized.

It will be understood from the foregoing description that the present invention provides a timing signal generator which comprises a first timing core 13a coupled to one of the magnetic poles of the rotor of a magneto generator serving as an ignitionpower supply, a second timing core 13b disposed closely adjacent to the first timing core 13a and coupled magnetically to a cupshaped body 10 forming the outer casing of the rotor, and a magnetically'shielded timing signal pickup means 4 disposed on a stationary base plate 16 so that the pole face portions of the timing cores 13a and 13b are cyclically brought opposite to the pickup means 4 during the rotation of the rotor. The present invention having such a structure is advantageous in that the rotor of the magneto generator can be used as the rotor of the timing signal generator thereby eliminating the necessity for separate provision of the latter rotor and the timing signal generator is small in size, compact in construction and inexpensive. Another advantage of the present invention resides in the fact that the utilization of the rotor of the ignition power supply generator as the rotor of the timing signal generator provides a high peripheral velocity and a sufficiently large output can be obtained even when the engine is rotating at a low speed. Further, according to the present invention, the timingsignal .pickup means 4 is magnetically-shielded so that a large variation occurs in the magnetic flux passing through the iron core 14b disposed within the magnetic shielding casing 14a when the timing cores 13a and 13b are brought to a position opposite to the iron core 14b during the. rotation of the rotor. This arrangement provides a further advantage in combination with a high peripheral velocity of the rotor in that the engine ignition timing can be satisfactorily stabilized. W

I claim! 1. An ignition timing pulse generator for use in a-contactless ignition system of an internal combustion engine including a magnetodynamo having a stator and a rotor, said 'rotor being housed by a generally annular body of magnetic material and having around its annular inner periphery a plurality of spaced, radially mangetized permanent magnets in contacttherewith, there being pole pieces respectively on the inner side of said magnets, said pulse generator including the improvement of: a v l a first timing core magnetically coupled to said annular body and extending generally radially inwardly therefrom magnetically insulatively adjacent a given one of said magnets to a point axially flush substantially with the opposite pole piece on said one magnet,

a second timing core magnetically coupled at one end to said one pole piece and having its other end spacedly disposed adjacent said first timing core to form a magnetic gap therebetween with opposite sides of different polarity, and

magnetically shielded timing signal pickup means disposed in said stator in a position to be brought opposite to said first and second timing cores during rotation of said rotor.

2. A magnetodynamo including a contactless ignition pulse generator with an internal combustion engine, said magneto-dynamo comprising:

a stator 'having at least one armature carrying coil means, i

a rotor having an annular body of magnetic material and being disposed concentrically of said rotor,

a plurality of radially polarized permanent magnets spacedly disposedabout the interior periphery of said annular body and in magnetic contact therewith, a like plurality of pole pieces respectively on the interior side of said magnets,

a first timing core magnetically coupled to one of said pole pieces and extending axially therefrom,

a second timing core magnetically coupled to said annular body'and extending radially inwardly therefrom to a point spacedly adjacent said first timing core and being magnetically insulated therefrom and from said one pole piece and its magnet, and

magnetically shielded timing signalpickup'means disposed in said stator at a position so that said first and second timing cores are cyclically brought opposite to said pickup means during rotation of said rotor. r

3'. A magnetodynamo as in claim 2 wherein said armature means has two opposite ends that are disposed in saidstator for magnetically bridging pole pieces of different polarity at one time in the cycle of rotor rotation and to be out of such magnetic bridging with such pole pieces at at least one other rotor'cycle time, said pickup means being disposed relative to said armature ends so that said pickup means is brought opposite to said first and second timing cores only during said other cycle time.

4. A magnetodynamo as in claim 2 wherein said first timing core extends axially from an edge of said one pole piece and has an opposite end which is substantially flush with said one pole piece, the end of said second timing core opposite said annular body being also substantially flush with said one pole piece.

5. A magnetodynamo as in claim 4 wherein said first timing core is straight and integral with said one pole piece.

6. A magnetodynamo as in claim 4 wherein at least one of said timing cores is notched and said rotor contains cast material axially of and between said magnets as at least an aid for holding said magnets and said one timing core in place.

respective 

1. An ignition timing pulse generator for use in a contactless ignition system of an internal combustion engine including a magnetodynamo having a stator and a rotor, said rotor being housed by a generally annular body of magnetic material and having around its annular inner periphery a plurality of spaced, radially mangetized permanent magnets in contact therewith, there being pole pieces respectively on the inner side of said magnets, said pulse generator including the improvement of: a first timing core magnetically coupled to said annular body and extending generally radially inwardly therefrom magnetically insulatively adjacent a given one of said magnets to a point axially flush substantially with the opposite pole piece on said one magnet, a second timing core magnetically coupled at one end to said one pole piece and having its other end spacedly disposed adjacent said first timing core to form a magnetic gap therebetween with opposite sides of different polarity, and magnetically shielded timing signal pickup means disposed in said stator in a position to be brought opposite to said first and second timing cores during rotation of said rotor.
 2. A magnetodynamo including a contactless ignition pulse generator with an internal combustion engine, said magneto-dynamo comprising: a stator having at least one armature carrying coil means, a rotor having an annular body of magnetic material and being disposed concentrically of said rotor, a plurality of radially polarized permanent magnets spacedly disposed about the interior periphery of said annular body and in magnetic contact therewith, a like plurality of pole pieces respectively on the interior side of said magnets, a first timing core magnetically coupled to one of said pole pieces and extending axially therefrom, a second timing core magnetically coupled to said annular body and extending radially inwardly therefrom to a point spacedly adjacent said first timing core and being magnetically insulated therefrom and from said one pole piece and its respective magnet, and magnetically shielded timing signal pickup means disposed in said stator at a position so that said first and second timing cores are cyclically brought opposite to said pickup means during rotation of said rotor.
 3. A magnetodynamo as in claim 2 wherein said armature means has two opposite ends that are disposed in said stator for magnetically bridging pole pieces of different polarity at one time in the cycle of rotor rotation and to be out of such magnetic bridging with such pole pieces at at least one other rotor cycle time, said pickup means being disposed relative to said armature ends so that said pickup means is brought opposite to said first and second timing cores only during said other cycle time.
 4. A magnetodynamo as in claim 2 wherein said first timing core extends axially from an edge of said one pole piece and has an opposite end which is substantially flush with said one pole piece, the end of said second timing core opposite said annular body being also substantially flush with said one pole piece.
 5. A magnetodynamo as in claim 4 wherein said first timing core is straight and integral with said one pole piece.
 6. A magnetodynamo as in claim 4 wherein at least one of said timing cores is notched and said rotor contains cast material axially of and between said magnets as at least an aid for holding said magnets and said one timing core in place. 